Well, the first line needs work, seems to be missing a word. The twins have distinct personalities, very good, but consider a physical description soon. It would be great to have spaces between sections of dialogue, but I understand that ficly is restrictive. :) I love the action and drama right at the beginning.
What terrible luck for Spencer to fall on that bee just moments after being persuaded to forgo the standard-issue bee repellant by his thoughtless brother! Considering the circumstances, I’d like to feel some sympathy for Spencer, but I find him so pathetically wet that I just can’t manage it.
Aside from these musings, it’s an interesting little story, but I think it could do with some streamlining – for instance, you have 10 "Spencer"s in there, and 8 "Nate"s: unnecessary repetition that will eat up your character allowance. I’d cut most of them out and use the extra characters to add a line break or two…